Flotation and/or cyanidation of gold ores are performed under optimum condition when the material is uniform in physical and metallic content. Basically, the blending at the processing plant is a key aspect of the metallurgical performance. In order to perform the blending, it is not necessary to hold the gold ore lot separate and the crushed material may be mixed on the backyard to build large blended stockpiles or each lot may be stored in individual fine ore bins and mixed with other material as they are taken for the mill feed. For example, if the lot is extremely large, blending may be done by mixing material on the backyard and feeding it directly to the processing plant from this stockpile.
Once the blending is performed, the ore assay may be performed from daily or shift composite samples from the sampling plant and conveyor belt mill feed samples. In some circumstances, blending is done during stockpiling operations by the manner in which the material is originally placed and taken from feed for the next stage. In this way, the original placement may be to build horizontal layers of different lots of material or to dump truck loads in alternate locations to make adjacent rows or long windrows. Then, the gold ore is moved from the stockpile in a direction counter to its placement and the mixture is obtained. This operation is repeated four to six times. In this way, control of gold ore grade is important. In other cases, stockpiles are built at the mill site in several ranges of gold content and the blending is performed by taking material from each stockpile in an established ratio in order to get a uniform feed grade.